Photosensitive silver fluoride element



Nov. 3', 1970 P. D. LUBIN ETAL 3,537,855

. PHOTOSENSITIVE SILVER FLUORIDE ELEMENT 7 Filed Oct. 5, 1966 2O- SUPPORT VACUUM DEPOSITION OF GOLD VACUUM DEPOSITION OF SILVER f f T f r f f r f ES'QWF' QJER BFB VAPOR FLUORIDE INVENTO #1412 0. M

United States Patent Office Patented Nov. 3, 1970 PHOTOSENSITIVE SILVER FLUORIDE ELEMENT Paul D. Lubin, Boston, and Joel M. Peisach, Hudson,

Mass., assignors to Polaroid Corporation, Cambridge,

Mass., a corporation of Delaware Filed Oct. 5, 1966, Ser. No. 584,412

Int. Cl. G03c 1/78 U.S. Cl. 9687 8 Claims ABSTRACT OF THE DISCLOSURE Photosensitive silver fluoride elements are prepared by the reaction of silver with boron trifluoride vapor under anhydrous conditions.

The present invention relates to novel photographic products, their production and use, and more particularly, to novel photosensitive elements, their production and use. Primary objects of the present invention are the production and use of novel photographic elements comprising photographic materials formed, at least in part, by the vacuum deposition of one or more of their components.

A further object of this invention is directed to the sensitization of a photographic support by the vacuum deposition of silver on appropriate substrate material followed by the treatment of said silver coated substrate with the vapor of boron trifluoride.

Other objects of the invention will, in part, be obvious and will, in part, appear hereinafter.

The invention accordingly comprises the several steps and the relation and order of one or more of such steps with respect to each of the others, and the product possessing the features, properties and the relation of elements which are exemplified in the following detailed disclosure, and the scope of the application which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

The figure shows successive, exaggerated diagrammatic cross-sectional views of materials being treated in accordance with the present invention.

The silver halide substrates that are formed by the process of this invention are quite unique and different from the prior art in that they contain some form of silver fluoride as the photosensitive material. Heretofore, the photographic art had generally considered silver fluorides not to be light sensitive and, therefore, of no importance in photography. Reference is made to Light Sensitive Systems by Jaromir Kosar, published 1965 by John Wiley & Sons, Inc., New York, with particular reference to pages 18 and 19. Silver fluoride is known to exist in three forms, namely, AgF, Ag F and AgF All of these are water-soluble. See the 41st edition Handbook of Chemistry and Physics, published by the Chemical Rubber Company at page 648. It is due to this water-solubility characteristic of silver fluoride that the prior art could not prepare a silver fluoride emulsion by the techniques usually employed with the other silver halides. It is seen, therefore, that the ability to prepare photosensitive silver fluoride strata by the process of the present invention whereby water is not present in the process is, therefore, unique and unexpected.

Generally, the process of the present invention involves the deposition of metallic silver upon a support and then subjecting the deposited silver to boron trifluoride vapors. The resultant stratum containing a silver fluoride resulting from this reaction of the silver with the vapors of the boron trifluoride, is formed of a large number of micro crystals which are supported on the substrate primarily by being adhered directly to each other and directly to the substrate. In one embodiment the silver may be vacuum deposited. In a particularly useful embodiment of the invention, one may first deposit by vacuum evaporation a layer of gold onto said support followed by the vacuum depositing of silver and the boron trifluoride vapor treatment. It should also be understood that the deposition of gold can occur prior to, simultaneously with, or subsequent to the vacuum deposition of the silver onto the substrate.

The support, or base bearing the silver stratum may be subjected to the boron trifiuoride treatment wherein the boron trifluoride is the sole gas utilized, or an inert carrier such as nitrogen vapor may be used together with said boron trifluoride. While the process of the present invention is primarily directed to the photographic art, it should not be construed as being limited thereto. In view of this it is seen that any silver coated base material such as a silver mirror or even a silver coin can be halogenated by the process of the present invention. Insofar as the photographic use of the present invention is concerned, the support materials utilizable for such include any suitable paper such as baryta paper, or any suitable plastic such as polyethylene terephthalate sold under the trade names Mylar or Cronar" by E. I. du Pont de Nemours & Company, Wilmington, Del. Excellent results can be obtained by the use of subbed Cronar film, i.e., a polyethylene terephthalate film subcoated with what is described as a water permeable, colloidal layer such as is set forth in US. Pat. Nos. 2,627,088 and 2,698,242.

The step of vacuum depositing involves evaporating silver at pressures below microns of mercury, and usually within the range of from 1X10 to 1X10- microns of mercury, these pressures being produced by continuous evacuation to insure the rapid removal of any gases produced during the vacuum deposition process. The stratum of silver laid down by the vacuum deposition upon the support may be as low as 10 mg. per square foot. Excellent results have been obtained wherein the silver coverage is within the range of 20 to 50 mg. per square foot. However, coverages of greater magnitude have been utilized. When it is desired to incorporate gold into the photosensitive element the gold may be vacuum deposited prior to, at the same time as, or subsequent to the vacuum deposition of the silver. Particularly beneficial gold coverages that have been utilized are within the range of 2 to 10 mg. per square foot of support material.

As has been emphasized before, the process of the present invention requires that the silver stratum or the gold and silver stratum be subjected to a fluorination treatment wherein no water is present. A desirable means of fluorination is the utilization of boron trifluoride vapor. The benefits to be derived from the use of this reagent are many. They include easy availability in commerce, relative ease of handling, the freedom from the toxicity of HF and F gases, the freedom from the need to use special reaction vessels which are impervious to the reagents and the fact that the commonly used photographic support materials are not degraded by BF while they are degraded by HF and F vapor.

The metallic stratum is subjected to the halogenation treatment for a period sufiicient to effect at least 30% halogenation, The thickness of the silver fluoride layer so formed is in the vicinity of of a micron thick. The formation of the silver fluoride is indicated by the fact that the transparent base coated sheet becomes translucent.

Photosensitive strata prepared in accordance with this invention may be developed by the application of heat; this method of development is disclosed and claimed in the US. Pat. No. 3,142,566 to Edwin H. Land, granted July 28, 1964.

It is seen that the photosensitive material of this-invention is binder-free, as distinguished from conventional.

gelatin-type photographic materials. In certaininstances,

it may be desirable to apply a stratum of a polymeric ma-,

terial over the surface of this binder-free photosensitive material, in which event the silver fluoride will still be substantially binder-free.

It has been found (as disclosed and claimed in thempending application of Joel M. Peisach, Ser. No. 584,447, filed Oct. 5, 1966), that the photosensitive stratum prepared by the process of the present invention may be developed to a negative silver image by exposure of the stratum to a light source containing ultraviolet radiation such as a xenon lamp or conventional photofiood, employing conventional print-out exposure techniques.

The following examples are set forth to illustrate this invention and are intended to be illustrative only.

EXAMPLE I The figure illustrates the production of a photosensitive element in accordance with the present invention. Gold was vacuum deposited by being evaporated uniformly onto sheet 20 of unsubbed Mylar film, approximately 0.014 inch thick, 4 /2 inches Wide and 15 inches long, to form a gold stratum 22 with a coverage of approximately 10 mg. per square foot. Then silver was vacuum deposited by being evaporated onto the support coated with gold to form a gold and silver stratum 24, with a coverage of about 60 mg. per square foot of silver.

This sheet was then placed in a desiccator, which was then evacuated at room temperature, The vacuum was broken by the introduction of 9 liters of boron trifluoride gas (equal to 27 grams of BF at room temperature and atmospheric pressure). The sheet was left in the boron trifluoride atmosphere for 20 hours. The so treated sheet was translucent, indicating the formation of a silver fluoride photosensitive stratum 26.

EXAMPLE II Silver was vacuum deposited by evaporation onto a sheet of Cronar film to provide a stratum having a silver coverage of approximately 20 mg. per square foot. This sheet was placed in a desiccator which was then evacuated at room temperature. The vacuum was broken by the introduction of boron trifluoride gas into the system. The sheet was left in this BP atmosphere for six hours. The sheet became translucent indicating the formation of a silver fluoride.

EXAMPLE III Silver was deposited by evaporation onto a sheet of baryta paper with a coverage of about 2 mg. per square foot. This sheet was placed in a desiccator which was then evacuated at room temperature. The vacuum was broken by the introduction of BF;, gas in conjunction with nitrogen gas as a carrier for'a total time of one hour. The sheet became translucent indicating the formation of silver fluoride.

EXAMPLE IV A photosensitive element prepared in accordance with Example I was exposed to long-Wave ultraviolet light from a Model X4 Blak Ray made by the Ultraviolet Products Company, Incorporated, San Gabriel, Calif, for

one minute at a distance oftwo inches. An image of moderate accutance of ahigh contrast object was visible immediately upon removal of the light source.

EXAMPLE V A photosensitive elementicomp rising silver fluoride on Mylar prepared in' accordance with the techniques de scribed above was exposed to alight source containing UV radiation for approximately one minute. This element was then subjected to heat within the range of 80 F. to 180 F. for about minutes to intensify the image.

'Photosensitive materials prepared in accordance with this invention are characterized by negligible grain, relatively low sensitivity, e.g., an exposure index of less than ASA 1, and by the formation of images exhibiting long,

soft or low contrast, curves.

Since certain changes may be made in the above products and processess without departing from the scope "of the invention herein involved, it is intended that all matter contained in the above description and shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

What is claimed is:

1. A process for fluorinating silver coated strata which comprises subjecting the silver coated stratum to boron trifluoride vapor under substantially anhydrous conditions.

2. A process for forming a photosensitive element, which comprises treating a silver coated photographic support with boron trifluoride vapor under substantially anhydrous conditions.

3. The process of claim 2 wherein the silver coated photographic support is prepared by the vacuum deposition of silver upon the support.

4. The process of claim 3 wherein gold is vacuum deposited in conjunction with the silver, prior to the boron trifluoride treatment.

5. The process of claim 2 wherein the support is selected from the group consisting of baryta paper and polyethylene terephthalate.

6. The process of claim 2 wherein nitrogen gas is employed as a carrier for the boron trifluoride vapor.

7. The process of claim 4 wherein the gold coverage is approximately 2 mg. per square foot and the silver coverage is approximately mg. per square foot.

8. The process of forming a photosensitive element which comprises the steps of vacuum depositing metallic gold onto a base of polyethylene terephthalate until a coverage of approximately 10 mg. per square foot is obtained; vacuum depositing metallic silver onto the gold coated base until a silver coverage of approximately 60 mg. per square foot is obtained; and subjecting the silvergold coated base to boron trifluoride vapor under substantially anhydrous conditions to form a photosensitive stratum containing a silver fluoride.

RONALD H. SMITH, Primary Examiner US. Cl. X.R. 

